Material for forming resin suitable for cutting, molded resin product as raw material for model, and method for manufacturing model

ABSTRACT

This invention relates to a machinable or grindable resin-forming material, comprising (A) a machinable or grindable resin or a precursor thereof, and (B) microcapsules comprising an encapsulated material (a) in liquid state and a wall material (b); wherein the machinable or grindable resin-forming material includes (B) at a ratio of 0.5 to 90 mass parts with respect to 100 mass parts of (A), and to a resin molded product for material of a model, which is formed by melting and solidifying or hardening and shaping the machinable or grindable resin-forming material. Accordingly, a machinable or grindable resin-forming material and a resin molded product for material of a model, in which the amount of scattering dust at the time of cutting or grinding the resin molded product is reduced, and a decrease in the strength is small, can be provided.

TECHNICAL FIELD

The present invention relates to a machinable or grindable (cuttable orgrindable) resin-forming material, a resin molded product for materialof a model, and a method for producing a model.

More specifically, the present invention relates to a resin moldedproduct for material of model, characterized in that when cutting orgrinding the resin molded product, the dust generated tends not to flyin the air and the working environment tends not to deteriorate; amachinable or grindable resin-forming material that provides the resinmolded product; and a method for producing a model with reduced amountof scattering dust.

BACKGROUND ART

A resin molded product for a material of a model such as a master modelor a mock-up model is supplied as a model or a mold, after being formedinto an arbitrary shape by cutting or grinding.

In recent years, because of various conditions such as a decrease in thenumber of wooden patternmakers, improvement in computers, therequirement for a shortened delivery period of model production, etc.,model production by cutting or grinding with an NC (numerical control)machine has become a major method.

The dust generated when cutting or grinding a resin molded product formaterial of a model by an NC machine causes contamination of the workingenvironment. Thus, the amount of generated dust may be reduced by amethod in which liquid with a low chemical activity such as an estercompound or an ether compound in which the hydroxyl groups at both endsof a (poly)oxyalkylene compound, e.g. a polyalkylene glycol, are blockedwith a fatty acid or a higher alcohol, is included in a resin(Publication of International Patent Application WO 98/17703).

However, this method may lead to a reduction in the strength of thematerial, and a finished model may be damaged or deformed easily.Therefore, although this method can be applied to a material of amock-up model that may have relatively low strength, it may not bedesirable to apply this method to a material of a master model or a moldthat requires strength.

As a result of intensive investigation to solve the above problem, theinventors have found that by including microcapsules containing anencapsulated material in a liquid state into a resin composition, it ispossible to obtain a resin molded product for material of a model, inwhich the amount of dust generated by cutting or grinding is small and adecrease in the strength is small. Thus, the present invention has beenaccomplished.

SUMMARY OF THE INVENTION

Thus, the present invention provides (I) to (IV) as follows:

-   -   (I) A machinable or grindable resin-forming material,        comprising (A) a machinable or grindable resin or a precursor        thereof; and (B) microcapsules comprising an encapsulated        material (a) in a liquid state and a wall material (b); wherein        the machinable or grindable resin-forming material includes (B)        at a ratio of 0.5 to 90 mass parts with respect to 100 mass        parts of (A).    -   (II) A resin molded product for material of a model, which is        formed by melting and solidifying or hardening and shaping the        material (I).    -   (III) A method for producing a model, which comprises cutting or        grinding the molded product (II).    -   (IV) Use of microcapsules (B) comprising an encapsulated        material (a) in a liquid state and a wall material (b) to reduce        the amount of scattering dust when cutting or grinding a resin        molded product for material of model.

DETAILED DESCLOSURE OF THE INVENTION

In the present invention, the encapsulated material (a) constituting themicrocapsules (B) is in a liquid state at 20° C. at 1 atm. Because acutting or grinding operation is often carried out mainly in a placewithout any temperature control equipment, to make (a) in a liquid statein the cold period, it is preferable that the freezing point of (a) isnot higher than −5° C., more preferably not higher than −10° C.

Because the temperature on the cutting or grinding face may increase dueto the heat of cutting or grinding by 70° C. or more depending on thecutting or grinding conditions, it is preferable that the boiling pointof (a) is not lower than 80° C., more preferably not lower than 120° C.

To cause (a) to scatter instantly at the time of cutting or grinding andallow it to adhere to the cut dust easily, it is preferable that theviscosity of (a) at 20° C. is not more than 5000 mPa·s, more preferablynot more than 3000 mPa·s, particularly preferably from 50 to 2500 mPa·s.

To reduce the amount of dust when cutting or grinding, it is necessarythat the machinable or grindable resin-forming material includes atleast 0.5 mass parts of (B) with respect to 100 mass parts of (A). Tomaintain the strength as a resin molded product for material of model,it is necessary that the machinable or grindable resin-forming materialincludes not more than 90 mass parts of (B) with respect to 100 massparts of (A). Taking into consideration that when the condition ofcutting or grinding is severe, part of (a) may not be able to adhere tothe dust, and may fall directly on the model, the NC machine, etc. otherthan the dust, and taking into account the ease and economic efficiencywhen including (B) into (A), it is more preferable that the machinableor grindable resin-forming material includes from 1 to 50 mass parts of(B) with respect to 100 mass parts of (A).

The encapsulated material (a) thus described is not particularly limitedas long as it is in a liquid state at 20° C. and has no adverse effecton (A). It includes those materials nonreactive with (A), and thosereactive with (A) but with no substantial influence on (A). Theencapsulated material (a) may be either a synthetic organic compound ora natural organic compound, and may be water-soluble or oil-soluble.Combinations of two or more kinds thereof also may be employed.

It is preferable that the number-average molecular weight of (a)measured by gel permeation chromatography is not more than 3000, morepreferably from 70 to 2500.

The synthetic organic compound used as (a) may be any of an aliphaticcompound, an alicyclic compound, and an aromatic compound.

Specific examples of the synthetic organic compound are hydrocarbonshaving a molecular weight of 70 to 250 (linear, branched or alicyclicsaturated aliphatic hydrocarbons, e.g. n-heptane, n-octane, isooctane,n-hexadecane, cyclohexane; unsaturated aliphatic hydrocarbons, e.g.1-octene; aromatic hydrocarbons, e.g. cumen), monohydric alcohols with amolecular weight of 100 to 270 (linear, branched or alicyclic aliphaticalcohols, e.g. 1-heptanol, n-nonyl alcohol, 2-ethylhexylalcohol;aromatic ring-containing alcohols, e.g. cuminic alcohol), dihydricalcohols (i.e. glycols) with a molecular weight of 60 to 270 (e.g.ethylene glycol, propylene glycol, 1,4-butanediol, etc.), alcoholshaving 3 to 6 hydroxyl groups and a molecular weight of 90 to 270(glycerol, trimethylolpropane, diglycerol, etc.), aliphatic or aromaticesters with a molecular weight of 130 to 500 (n-nonyl acetate, octylacetate, isoamyl butyrate, di-2-ethylhexyl adipate, benzyl acetate,dibutyl phthalate, etc.), ketones with a molecular weight of 100 to 270(methyl amyl ketone, 2-octanone, 3-octanone, etc.), mono or dietherswith a molecular weight of 70 to 300 {diisobutyl ether, diisoamyl ether,benzyl ethyl ether, monoalkyl ethers (1 to 8 carbon atoms in themonoalkyl group) of the above-described glycols (e.g. “ethylcellosolve”(β-hydroxydiethyl ether)), dialkyl ethers (the alkyl group of the“dialkyl” has 1 to 8 carbon atoms) of the above-described glycols (e.g.ethylene glycol diethyl ether), etc.}, and polyethers with anumber-average molecular weight of not more than 3000 {polyethyleneglycol, polypropylene glycol, propylene oxide adducts to glycerol (notmore than 50 moles adducts), (hereinafter, “propylene oxide” isabbreviated as “PO”), PO adducts to pentaerythritol (not more than 50moles adducts), polyoxyalkylene monoalkyl ethers (the “polyoxyalkylene”group has 2 to 4 carbon atoms in the alkylene group, the“polyoxyalkylene” segment has a polymerization degree of not more than66; these also apply to the polyoxyalkylene groups in the followingcompounds; and the monoalkyl group has 1 to 8 carbon atoms),polyoxyalkylene dialkyl ethers (the alkyl group in the “dialkyl” has 1to 8 carbon atoms), polyoxyalkylene alkyl phenyl ethers (the alkyl grouphas 1 to 8 carbon atoms), aliphatic acid mono and/or diesters ofpolyalkylene glycols (the polyalkylene glycol segment has apolymerization degree of not more than 66, an aliphatic acid residue has12 to 24 carbon atoms), polyoxyethylene polyoxypropylene block polymers,etc.).

Among these synthetic organic compounds, hydrocarbons, alcohols, estersand polyethers are preferred from the aspect of stability, safety andsanitation. More preferred are saturated aliphatic hydrocarbons with amolecular weight of 70 to 250.

Natural organic compounds used as (a) include mineral oils or purifiedproducts thereof (spindle oil, liquid paraffin, etc.), plant oils (oliveoil, castor oil, rape seed oil, etc.), animal oils (sperm oil, beef oil,squalene, etc.), and purified or modified products of these animal andplant oils (purified castor oil, polyhydric alcohol-modified castor oil,squalane, etc.).

Among these natural organic compounds, and also among all examples of(a), mineral oils, animal and plant oils, and modified products thereofare preferred in the aspect of availability and cost.

The wall material (b) constituting (B) is not particularly limited, andthermoplastic resins, thermosetting resins, etc. may be used as (b).

The thermoplastic resins include styrene-based resins (polystyrene,acrylonitrile-styrene resins, acrylonitrile-butadiene-styrene resins,styrene-butadiene resins, etc.), polyamide resins (6-nylon, 66-nylon,12-nylon, etc.), polyethylene-based resins {polyethylene,ethylene-α-olefin copolymers (the α-olefin has 3 to 6 carbon atoms),ethylene-vinyl acetate copolymers, etc.}, polypropylene-based resins{polypropylene, propylene-α-olefin copolymers (the α-olefin has 4 to 6carbon atoms), etc.}, (meth)acrylic resins {alkyl acrylate polymershaving 1 to 12 carbon atoms in the alkyl group, alkyl methacrylatepolymers having 1 to 12 carbon atoms in the alkyl group, etc.},polyacrylonitrile, thermoplastic polyester resins (polyethyleneterephthalate, polybutylene terephthalate, polycarbonate, etc.),thermoplastic polyurethane resins, polyoxyalkylene-based resins having 2to 4 carbon atoms in the alkylene group, polyacetal resins, polyvinylchloride, polyvinylidene chloride, and polyphenylene sulfide resins.Combinations of two or more kinds thereof also may be used.

The thermosetting resins include epoxy resins (e.g. epoxy resins such asbisphenol epoxy resins, novolak epoxy resins and alicyclic epoxy resinscured with polyamines, acid anhydrides, etc.), unsaturated polyesterresins (e.g. crosslinked copolymers of unsaturated polyesters derivedfrom glycol, unsaturated dibasic acids and saturated dibasic acids withother vinyl monomers), phenol resins (e.g. phenol-formaldehyde resins,phenol-furfural resins), polyimide resins, thermosetting polyurethaneresins, melamine resins, urea resins, etc. Combinations of two or morekinds thereof also may be used.

Among the thermoplastic resins, polyacrylonitrile and (meth)acrylicresins, copolymers thereof, and vinylidene chloride resins arepreferred. Among the thermosetting resins, phenol resins are preferred.

Among these, polyacrylonitrile, alkyl acrylate polymers, alkylmethacrylate polymers, and copolymers thereof are more preferred fromthe aspect of good machinability or grindability.

When the wall material (b) is a thermoplastic resin, because of theincreased temperature due to the cutting or grinding heat, it ispreferable that the melting point of (b) is at least 100° C. Consideringsevere conditions of cutting or grinding, it is more preferable that themelting point is from 120° C. to 250° C.

It is preferable that (b) is used with a film thickness of 0.01 to 100μm.

The method of producing the microcapsules (B) is not particularlylimited, and any conventional method may be employed. Representativeexamples of the production method are coacervation, interfacialpolymerization, in-situ polymerization, etc.

Coacervation is used widely. For example, microcapsules including anencapsulated material such as colorless dye for copy paper or liquidcrystal, etc. with gelatin as a wall material are produced bycoacervation.

In the interfacial polymerization, a polymerization reaction is causedat the interface between an aqueous phase including a hydrophilicmonomer and an oil phase including a lipophilic liquid to formmicrocapsules. Many microcapsules using polyurethane, polyurea, epoxyresins, etc. as wall materials are produced by this method.

In in-situ polymerization, a monomer and a catalyst are included ineither of two phases that are immiscible with each other, and themonomer is polymerized at the interface so as to form a uniform film onthe surface of an encapsulated material. As the wall material,copolymers of styrene and maleic anhydride, copolymers of ethylene andmaleic anhydride, arabic rubber, polyacrylic acid, acrylic acid/acrylicacid ester copolymers, melamine-formalin resins, polyurethane resins,etc. may be used.

Microcapsules produced by interfacial polymerization and in-situpolymerization are favorable as (B) from the aspect of the ranges ofselection of the wall material, the encapsulated material and theparticle size, and the stability of the capsules. From the aspect ofcost, microcapsules produced by in-situ polymerization are morepreferred.

The surface of (B) may be coated with an inorganic filler, e.g. talc,calcium carbonate, etc.

Because of the ease of handling and less decrease in the strength whenincluded in the resin composition, it is preferable that thevolume-average particle size (median) of (B) measured by a laserdiffraction type particle-size distribution measuring apparatus is from1 μm to 1500 μm, more preferably from 3 μm to 1000 μm.

When considering economic efficiency and handling properties, it ispreferable that the amount z of the encapsulated oil in (B), which isexpressed by the equation z=x×100/y [z is the amount (volume %) of anencapsulated oil per one microcapsule; x is the volume of theencapsulated material (a) contained in one microcapsule; y is the volumeof one microcapsule] is at least 40 volume %, more preferably from 50 to90 volume %. The “encapsulated oil” herein refers to the encapsulatedmaterial (a).

The machinable or grindable resin or a precursor thereof (A) is notparticularly limited as long as it is to be a resin having machinabilityor grindability. For example, the precursors of thermosetting resinsexemplified above for use as (b) may be employed. Further, thethermoplastic resins exemplified above for use as (b) may be employed.The resin of (b) may be either the same as or different from (A) or aresin obtained from (A).

When (A) is a thermoplastic resin, it is preferable that the meltingpoint of (A) is not higher than 180° C., more preferably from 120° C. to160° C. When the melting point is higher than 180° C., the microcapsulesmight dissolve during the production of a compound or during molding.

Among these precursors of thermosetting resins and the thermoplasticresins, preferred are those to become hard resins with a Shore Dhardness of at least 60 (particularly between 62 and 95) when used aloneand subjected to reaction hardening (in the case of thermosettingresins) or melting and solidifying (in the case of thermoplastic resins)without decreasing their densities by foaming, etc. Such resins includeepoxy resins, rigid polyurethane resins, acrylonitrile-butadiene-styreneresins, polyethylene-based resins, polypropylene-based resins, and thelike.

Because of the wide range of selection for raw material components thatallows suitable use for various properties required for a resin moldedproduct for material of model, ease of mixing with the microcapsules (B)and below-described additive (C), and ease of molding, precursors ofepoxy resins and rigid polyurethane resins are more preferred as (A).Particularly preferred are precursors of rigid polyurethane resins. Therigid polyurethane resins are favorable, because an additive (C) can bemixed in raw materials comprising a polyol component and an organicpolyisocyanate component, and the mixture can be hardened and shapedinto a desired form.

The above-mentioned precursors of epoxy resins usually comprise acommonly used polyepoxide having at least two epoxy groups in onemolecule and a polyamine-based hardening agent or an acidanhydride-based hardening agent.

Examples of the polyepoxide include polyglycidyl ethers obtained byreacting an epihalohydrin (e.g. epichlorohydrin) or a dihalohydrin (e.g.glycerol dichlorohydrin) with a polyhydric (2 to 6 hydroxyl groups ormore) phenols having 6 to 50 carbon atoms or more {e.g. bisphenol A,bisphenol F, 1,1-bis(4-hydroxyphenyl)ethane, resorcinol, hydroquinone,catechol, nuclear-substituted products thereof, halogen compoundsthereof, etc.} or a polyhydric (2 to 6 hydroxyl groups or more) alcoholshaving 2 to 100 carbon atoms {e.g. alkane polyols (e.g. ethylene glycol,propylene glycol, 1,3-butanediol, 1,4-butanediol, trimethylolpropane,glycerol, pentaerythritol), polyalkylene glycols having a number-averagemolecular weight of not more than 3000 (2 to 4 carbon atoms in thealkylene group) (e.g. diethylene glycol, triethylene glycol,tetraethylene glycol, polyethylene glycol), etc.}; or polyglycidylesters obtained by reacting an epihalohydrin or a dihalohydrin with analiphatic or aromatic polycarboxylic acid having 6 to 20 carbon atoms ormore and having 2 to 6 carboxyl groups or more (e.g. oxalic acid,fumaric acid, maleic acid, succinic acid, glutaric acid, adipic acid,phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalicacid, and halogen compounds thereof).

Among these, polyglycidyl ethers of polyhydric phenols are preferred,and glycidyl ethers of bisphenol A, bisphenol F, and1,1-bis(4-hydroxyphenyl)ethane are more preferred. Furthermore, thosehaving a viscosity at 25° C. of not more than 15,000 mPa·s and an epoxyequivalent of 180 to 200 are preferred.

Examples of the polyamine-based hardening agent include aliphaticpolyamines having 2 to 18 carbon atoms, alicyclic polyamines having 4 to15 carbon atoms, aromatic polyamines having 6 to 20 carbon atoms,heterocyclic polyamines having 4 to 15 carbon atoms,polyamideamine-based hardening agents, etc.

The aliphatic polyamines include alkylenediamines having 2 to 6 carbonatoms (e.g. ethylenediamine, propylenediamine, tetramethylenediamine),polyalkylene polyamines (dialkylenetriamines to hexaalkyleneheptaminehaving 2 to 6 carbon atoms in the alkylene group) (e.g.diethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine, iminobispropylamine, bis(hexamethylene)triamine},substituted products thereof with an alkyl group having 1 to 4 carbonatoms or a hydroxyalkyl group having 2 to 4 carbon atoms {e.g.dialkylaminopropylamine (1 to 4 carbon atoms in the alkyl group of the“dialkyl”), diethylaminopropylamine, aminoethylethanolamine}, diethyleneglycol bispropylenediamine, aromatic ring-containing aliphaticpolyamines having 8 to 15 carbon atoms (e.g. metaxylylenediamine).

The alicyclic polyamines include isophoronediamine,bis(4-amino-3-methylcyclohexyl)methane, etc.

The aromatic polyamines include metaphenylenediamine,diaminodiphenylmethane, etc.

The heterocyclic polyamines include N-aminoethylpiperazine, etc.

The polyamideamine-based hardening agents include those obtained byreacting a dimer acid containing a polymerized aliphatic acid having 36carbon atoms as a main component, with an excessive amount (at least 2moles per one mole of the acid) of a polyamine (e.g. the above-describedalkylenediamines and polyalkylenepolyamines). The dimer acid is producedby heat polymerizing an unsaturated fatty acid containing linoleic acidor oleic acid as a main component in the presence of a catalyst.

Examples of the acid anhydride-based hardening agents include aromaticacid anhydrides {e.g. phthalic anhydride, trimellitic anhydride,ethylene glycol bis(anhydrotrimellitate), glyceroltris(anhydrotrimellitate), pyromellitic anhydride,3,3′,4,4′-benzophenonetetracarboxylic acid anhydride}, aliphatic acidanhydrides (maleic anhydride, succinic anhydride, tetrahydro phthalicanhydride, methyltetrahydro phthalic anhydride, “nadic methyl anhydride”(methyl-5-norbornene-2,3-dicarboxylic anhydride), alkenyl succinicanhydrides having 8 to 12 carbon atoms in the alkenyl group, hexahydrophthalic anhydride, methylhexahydro phthalic anhydride,methylcyclohexenetetracarboxylic acid anhydride, polyadipic acidanhydride (weight-average molecular weight: 750 to 850), polyazelaicacid anhydride (weight-average molecular weight: 1200 to 1300), andpolysebacic acid anhydride (weight-average molecular weight: 1600 to1700).

Among these hardening agents, polyamine-based hardening agents arepreferred, and aliphatic polyamines having 2 to 18 carbon atoms are morepreferred. Furthermore, those having a viscosity at 25° C. of not morethan 15,000 mPa·s are preferred.

It is preferable that the ratio of these hardening agents used isbetween 0.25 and 2.0, more preferably between 0.5 and 1.75 equivalent ofa hardening agent with respect to epoxy equivalent.

The above-mentioned precursors of rigid polyurethane resins usuallycomprise a polyol component and an isocyanate component.

Examples of the polyol component used in the polyurethane resin includepolyether polyols, polyester polyols, and other polyols.

The polyether polyols include, for example, compounds in which analkylene oxide is added to a compound having at least two (preferablyfrom 3 to 8) active hydrogen atoms, e.g. polyhydric alcohols, polyhydricphenols, amines, polycarboxylic acids and phosphoric acids, and mixturesthereof.

Among the polyhydric alcohols, those having 2 to 8 hydroxyl groups arepreferred, and combinations of two or more kinds thereof also may beused. Specific examples are aliphatic dihydric alcohols having 2 to 12carbon atoms, e.g. ethylene glycol, propylene glycol, 1,4-butanediol anddiethylene glycol; aliphatic alcohols having 3 to 8 hydroxyl groups andhaving 3 to 12 carbon atoms, e.g. glycerol, trimethylolpropane,pentaerythritol, methylglucoside, diglycerol, sorbitol and sucrose;alicyclic alcohols having 6 to 18 carbon atoms, e.g. cyclohexyleneglycol, cyclohexane dimethanol; aromatic alcohols having 8 to 20 carbonatoms, e.g. 1,4-bis(hydroxyethyl)benzene; and the like.

Examples of the polyhydric phenol include hydroquinone, bisphenols (e.g.bisphenol A, bisphenol F), condensed products of phenol andformaldehyde, etc.

Aliphatic amines among the amines include alkanolamines (e.g.diethanolamine, triethanolamine), alkylamines having 1 to 20 carbonatoms in the alkyl group (e.g. ethylamine), alkylenediamines having 2 to6 carbon atoms in the alkylene group (e.g. ethylenediamine,hexamethylenediamine), polyalkylenepolyamines {dialkylenetriamines tohexaalkyleneheptamines having 2 to 6 carbon atoms in the alkylene group(e.g. diethylenetriamine, triethylenetetramine)}, etc.

Further examples of the amines include aromatic amines having 6 to 20carbon atoms (e.g. toluenediamine, diphenylmethanediamine), alicyclicamines having 4 to 15 carbon atoms (e.g. isophoronediamine,cyclohexylenediamine), and heterocyclic amines having 4 to 15 carbonatoms (e.g. aminoethylpiperazine), etc.

As the polycarboxylic acids, those described below may be used.

Among these, polyhydric alcohols are preferred.

As the alkylene oxide that is added to an active hydrogenatom-containing compound, those having 2 to 8 carbon atoms arepreferred. Specific examples are ethylene oxide (EO), PO, 1,2-, 2,3-,1,4- or 2,4-butylene oxide, styrene oxide, and the like, andcombinations thereof (by block and/or random addition). Among these, POand combinations of EO and PO are particularly preferred.

Specific examples of the polyether polyols are PO adducts of glycerol,trimethylolpropane, triethanolamine, pentaerythritol, sorbitol andsucrose.

Examples of the polyester polyols include condensed polyester polyolsfrom polycarboxylic acids and polyols, and lactone polyester polyolsformed by ring-opening polymerization of lactone.

The polycarboxylic acids include aliphatic dicarboxylic acids having 2to 10 carbon atoms or anhydrides thereof (e.g. adipic acid, sebacicacid, maleic anhydride), aromatic polycarboxylic acids having 8 to 14carbon atoms and having 2 to 4 carboxyl groups in the aromatic ring(e.g. phthalic anhydride, terephthalic acid, trimellitic acid,pyromellitic acid), etc. Preferred are phthalic anhydride andterephthalic acid. The polyols include the polyhydric alcohols describedin the above section of polyether polyols, and low molar (usually from 1to 3 moles) alkylene oxide adducts thereof. Preferred are 1,4-butanediol, ethylene glycol, and diethylene glycol.

Specific examples of the condensed polyester polyols arepoly(1,4-butanediol adipate), poly(1,4-butanediol terephthalate) andpoly(diethylene glycol) terephthalate.

As the lactone in the lactone polyester polyols, usually a lactonehaving 3 to 7 carbon atoms is used, e.g. ε-caprolactone,δ-valerolactone, etc. Preferably ε-caprolactone is used. A specificexample of the lactone polyester polyols is poly(ε-caprolactone) polyol.

Other polyols include polyether polyols grafted with a homopolymer or acopolymer of vinyl compounds such as acrylonitrile, styrene and methylmethacrylate; polybutadiene polyols; hydroxyl-containing vinyl polymers;etc.

The hydroxyl value of each polyol exemplified above is preferably from200 to 700, more preferably from 250 to 600. When the hydroxyl value isat least 200, the obtained polyurethane molded product has heatresistance and strength. When the hydroxyl value is not more than 700,scorching is not caused by the reaction heat during molding, and theobtained molded product has good machinability or grindability.

As the polyol component, polyols having a hydroxyl value of less than200 [e.g. high molecular weight polyether polyols, castor oils (e.g.castor oil and polyol-modified castor oils), etc.], polyols having ahydroxyl value of more than 700 (e.g. those exemplified as polyhydricalcohols in the above section of polyether polyols), and polyamines(e.g. diethyltolylenediamine, 2,2′,3,3′-tetrachloro-4,4′-diaminodiphenylmethane), etc. may be used with apolyol having the above-specified hydroxyl value to the extent so thatthe characteristics required as a material for cutting or grinding arenot impaired, preferably in the range of not more than 30 mass % withrespect to the polyol having the above-specified hydroxyl value.

Among the examples of the polyol component, preferred are polyetherpolyols, particularly alkylene oxide adducts to polyhydric alcohols.Particularly preferred are PO adducts of glycerol, trimethylolpropane,triethanolamine, pentaerythritol, sorbitol and sucrose.

As the organic polyisocyanate component, those conventionally used inthe production of urethane foams may be used.

Examples of such isocyanate include aromatic polyisocyanates, aliphaticpolyisocyanates, alicyclic polyisocyanates and araliphaticpolyisocyanates, and modified products thereof (e.g. modified withcarbodiimide, allophanate, urethane, urea, biuret, isocyanurate,oxazolidone, etc.), and mixtures of at least two or more kinds thereof.

The aromatic polyisocyanates include aromatic diisocyanates having 6 to16 carbon atoms (except the carbon in the NCO group; this also appliesto the following polyisocyanates), aromatic triisocyanates having 6 to20 carbon atoms, and crude products of these isocyanates, etc. Specificexamples are 1,3- and 1,4-phenylene diisocyanates, 2,4- and 2,6-tolylenediisocyanates (TDI), crude TDI, 2,4′- and 4,4′-diphenylmethanediisocyanates (MDI), polymethylene polyphenyl isocyanates (crude MDI),naphthylene-1,5-diisocyanate, triphenylmethane-4,4′, 4″-triisocyanate,etc.

The aliphatic polyisocyanates include aliphatic diisocyanates having 6to 10 carbon atoms, etc. Specific examples are 1,6-hexamethylenediisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, lysinediisocyanate, etc.

The alicyclic polyisocyanates include alicyclic diisocyanates having 6to 16 carbon atoms, etc. Specific examples are isophorone diisocyanate,4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate,norbornane diisocyanate, etc.

The araliphatic isocyanates include araliphatic diisocyanates having 8to 12 carbon atoms, etc. Specific examples are xylylene diisocyanate,α,α,α′,α′-tetramethylxylylene diisocyanate, etc.

Specific examples of the modified polyisocyanates are urethane-modifiedMDI, carbodiimide-modified MDI, sucrose-modified TDI, castoroil-modified MDI, etc.

Among these, aromatic polyisocyanates are preferred, and polymethylenepolyphenyl isocyanates are particularly preferred.

The ratio of the polyol component to the organic polyisocyanatecomponent when producing a polyurethane resin may be varied. From theaspect of the strength of the resin, it is preferable that theisocyanate index [equivalent ratio of (NCO groups/active hydrogenatom-containing groups)×100] is between 80 and 140, more preferablybetween 85 and 120.

The reaction method may be either a one-shot method or a prepolymermethod in which part of a polyol component is preliminarily reacted withan organic polyisocyanate component.

By including an additive (C) in (A) as needed, a more favorable resinmolded product for material of model may be formed.

Examples of the additive (C) include fillers, dehydrating agents,lubricants, foam stabilizers, defoaming agents, catalysts, coloringagents, flame retardants, age resistors, plasticizers, etc.

A filler (C1) may be added to increase the strength and the thermaldimensional stability of the resin composition or to reduce the weightof the resin composition.

Examples of (C1) include metal powder or fiber (iron powder, aluminumpowder, etc.), inorganic powder or fiber (powder or fiber of glass,carbon, ceramics, talc, calcium carbonate, etc.), powder or fiber formedof a polymer (powder or fiber of vinylon, “Kevlar” (manufactured by DuPont), an acrylic resin, etc.), hollow microspheres (glass microballoon,acrylic microballoon, phenolic microballoon, etc.), etc.

In a resin molded product for material of model that requires strengthand/or thermal dimensional stability, it is preferable to use a metalpowder, an inorganic powder or a fiber, more preferably an inorganicpowder. To reduce the weight of the resin composition, it is preferableto use hollow microspheres. Among them, acrylic microballoon andphenolic microballoon are preferred.

It is preferable that the mixed amount of (C1) is not more than 80 massparts, more preferably from 0.5 to 60 mass parts, particularlypreferably from 1 to 50 mass parts with respect to 100 mass parts of(A).

As the additive (C), lubricants (e.g. calcium stearate, ethylenediaminedistearylamide), foam stabilizers (silicone-based foam stabilizers, e.g.polyoxyalkylene dialkyl polysiloxane), defoaming agents (e.g. dimethylsiloxane copolymer, silicone), catalysts (amine-based catalysts, e.g.triethylenediamine; metal-based catalysts, e.g. dibutyl tin dilaurate;etc.), coloring agents (e.g. metal oxide, dis-azo pigment), flameretardants (e.g. phosphoric acid ester, antimony oxide), age resistors(e.g. nickel dibutyldithiocarbamate, hindered phenol), plasticizers{phthalic acid dialkyl esters (the alkyl group in the “dialkyl esters”has from 1 to 10 carbon atoms), e.g. dibutyl phthalate; adipic aciddialkyl esters (the alkyl group in the “dialkyl esters” has from 1 to 10carbon atoms), e.g. di-2-ethylhexyl adipate; etc.}, and in the case ofpolyurethane resins, dehydrating agents (e.g. calcium sulfate, molecularsieve), etc. may be added further as appropriate.

It is preferable that the amount of a lubricant mixed is not more than20 mass parts, more preferably from 0.2 to 15 mass parts with respect to100 mass parts of (A).

It is preferable that the amount of a plasticizer mixed is not more than20 mass parts, more preferably from 0.2 to 10 mass parts with respect to100 mass parts of (A).

It is preferable that the amount of a catalyst mixed is not more than 1mass part, more preferably from 0.005 to 0.2 mass parts with respect to100 mass parts of (A).

It is preferable that the amount of a dehydrating agent mixed is notmore than 10 mass parts, more preferably from 0.2 to 8 mass parts withrespect to 100 mass parts of (A).

It is preferable that the amount of a foam stabilizer, a defoamingagent, a coloring agent, a flame retardant or an age resistor mixed iseach not more than 3 mass parts, more preferably from 0.1 to 2 massparts with respect to 100 mass parts of (A).

The method for producing a machinable or grindable resin-formingmaterial of the present invention from a machinable or grindable resinor a precursor thereof (A) and microcapsules (B) is not particularlylimited, as long as (B) are dispersed uniformly in (A). For example, (B)may be mixed in a part of a thermoplastic resin or a precursor of athermosetting resin using a planetary mixer, a kneader, a hand mixer, avertical mixing vessel with mixing blades or the like. Among thesemixing apparatuses, a planetary mixer is preferred.

When using an additive (C), in the above-described manner, (C) also maybe mixed and dispersed in (A). Thus, (B) and (C) may be mixed anddispersed in (A) simultaneously by the above-described method.

In the case of a thermoplastic resin, a method in which powder of athermoplastic resin is mixed with microcapsules (B) as powder, and thenthe mixture is heated at the time of molding to melt the thermoplasticresin may be employed. Or a method in which microcapsules (B) are putinto a preliminarily melted thermoplastic resin and mixed in it may beemployed. The preferred method is mixing both powders with each other.

In the case of a thermosetting resin, for example, when obtaining aresin molded product for material of model comprising a thermosettingpolyurethane resin, a method in which microcapsules (B) are dispersed inthe above-described polyol component, and thereafter the dispersion isreacted with the organic polyisocyanate component by a conventionalmethod may be employed. Or a method in which microcapsules (B) aredispersed in the organic polyisocyanate component, and thereafter thedispersion is reacted with the polyol component may be employed. Theformer method is preferred.

A resin molded product for material of model according to the presentinvention can be obtained, when (A) is a thermoplastic resin, by meltingand solidifying a machinable or grindable resin-forming material of thepresent invention at a temperature of not lower than its melting point;and when (A) is a thermosetting resin, by hardening and shaping amachinable or grindable resin-forming material of the present invention.

When producing a resin molded product for material of model comprising athermoplastic resin, it can be produced continuously using aconventional extruder (single-screw or twin-screw extruder), acontinuous kneader or the like after mixing (A) and (B).

The resin molded product for material of model may be a resin foamedmolded product having a density of 0.05 to 0.95 g/cm³, a molded productcomposed of almost only a resin and having a density of 0.95 to 1.25g/cm³, or a non-foamed molded product containing an inorganic filler andhaving a density of 1.25 to 2 g/cm³. It is preferable that the resinmolded product for material of model is a foamed resin so as to improveits machinability or grindability by decreased density. A polyurethaneresin foamed molded product is particularly preferred in that itsdensity can be decreased easily by foaming.

When obtaining a foamed molded product, for example, in the case offoaming a polyurethane resin, a foaming method using a blowing agent maybe employed. In this method, a volatile blowing agent such asfluorocarbon, hydrogen atom-containing halogenated hydrocarbon or a lowboiling point hydrocarbon, or water as a source of generating carbondioxide gas, etc. is added during and/or before the mixing of a polyolcomponent with an organic polyisocyanate component. Also, a mechanicalfroth foaming method may be employed in which an inactive gas such asair or nitrogen is blown during the mixing of the above-describedcomponents.

The mechanical froth foaming method is particularly preferred in thatthe bubbles after foaming have a small size and are dispersed uniformly,and the density distribution in the obtained cured product is uniform.

In the mechanical froth foaming method, a mechanical froth foamingmachine comprising a cylindrical stator having many gear teeth on itsinner surface and a rotor having many gear teeth and provided within thestator is used, and a liquid to be foamed and an inactive gas are fedinto the foaming machine simultaneously and continuously while rotatingthe rotor, and thereby a foamed liquid is taken out of the foamingmachine continuously through an outlet. This method can be applied tothe foaming of thermosetting resins other than polyurethane. Becauseinlets for liquids and inactive gases can be provided as needed, mixingof two or more kinds of liquids and inactive gases is possible. Theliquid may have hardenability if it hardens after being discharged fromthe foaming machine.

It is preferable that the volume of the microbubbles of an inactive gasformed by the mechanical froth foaming method is from 10% to 70%, morepreferably from 20% to 60% with respect to the volume of the moldedproduct (total volume of the inactive gas and the resin molded product).When it is at least 10%, machinability or grindability is excellent,since machinability or grindability is improved by decreased density.When it is not more than 70%, uniformly dispersed fine bubbles are easyto obtain, and properties as a resin molded product for material of amodel are excellent.

Because little dust scatters at the time of cutting or grinding, theresin molded product for material of a model according to the presentinvention may be cut or ground by an NC machine or the like, and usedsuitably as a material of a model such as a mock-up model that is a realsize model of an automobile or a household electric appliance, or amaster model to be an original pattern of a mold.

The conditions of cutting or grinding a material with an NC machine areas follows: For example, in the case of an end mill using a cutter witha diameter of 20 mm, the cutter is rotated at 1000 rpm to 10,000 rpm,and the feed rate is approximately from 1000 mm/min to 10,000 mm/min.

The present invention is described further with reference to thefollowing examples; however, the present invention is not limited tothese examples. The parts in the examples are based on mass.

[Used Raw Materials]

Microcapsules (B1): Microcapsules having an average particle size of 500μm and containing 60% of encapsulated oil, and comprising anencapsulated material of squalane and a wall material of polymethylmethacrylate (“Matsumoto Microsphere SQH”, manufactured by MATSUMOTOYUSHI-SEIYAKU CO., Ltd.)

Microcapsules (B2): Microcapsules having an average particle size of 35μm and containing 80% of an encapsulated oil, and comprising anencapsulated material of a liquid paraffin and a wall material ofpolymethyl methacrylate (“Matsumoto Microsphere MO”, manufactured byMATSUMOTO YUSHI-SEIYAKU CO., Ltd.)

Dust-scattering reducer: polyethylene glycol dioleate (thenumber-average molecular weight of the polyethylene glycol: 600).

Polyol: Polyether polyol having a hydroxyl value of 400 in which PO isadded to glycerol.

Organic polyisocyanate: Polymethylene polyphenyl isocyanate (“MillionateMR-200”, manufactured by NIPPON POLYURETHANE INDUSTRY CO., LTD.)

Inorganic filler (C1): Calcium carbonate (“Whiton SB”, manufactured byShiraishi Calcium Co., Ltd.)

Hollow microsphere (C2): Acrylic microballoon with an average particlesize of 20 μm and a density of 0.24 (“Matsumoto Microsphere MFL-80GCA”,manufactured by MATSUMOTO YUSHI-SEIYAKU CO., Ltd.)

Dehydrating agent (C3): Molecular sieve (“Molecular Sieve 3A–B Powder”,manufactured by UNION SHOWA K.K.)

Foam stabilizer (C4): Silicone-based foam stabilizer (“SZ-1931”,manufactured by NIPPON UNICAR COMPANY, LTD.)

Catalyst (C5): Di-n-butyl tin dilaurate (“StannBL”, manufactured bySANKYO ORGANIC CHEMICALS CORPORATION).

-   [Amount of scattering dust]: A molded product was cut with a    bandsaw, and 5 g of the sawdust generated at this time was put in a    300 ml glass bottle, and then the bottle was capped. The bottle was    shaken vigorously up-and-down several times and allowed to stand    still, and 3 seconds later, evaluation of ◯, Δ and X was made based    on the amount of the dust flying in the bottle. The symbol ◯    indicates that little dust is flying; Δ indicates that a small    amount of dust is flying; and X indicates that a considerable amount    of dust is flying.-   [Bending strength]: In accordance with JIS K6911, bending strength    was measured using “Shimadzu AUTOGRAPH AGS-500A” manufactured by    Shimadzu Corporation.-   [Izod impact strength]: In accordance with JIS K6911, Izod impact    strength was measured using “Izod impact tester” manufactured by    TOYO SEIKI SEISAKU-SHO, Ltd. (no notch).

EXAMPLES 1 TO 5

With the recipe described in Table 1, respective materials were put in aplanetary mixer, and stirred at 130 rpm for 10 minutes. Thereafter, itwas defoamed by stirring at not more than 30 mmHg for 5 minutes toobtain a polyol component. An isocyanate component also was obtained inthe same manner.

Next, the polyol component and the isocyanate component were fed into aplanetary mixer at the ratio specified in Table 1 so that the totalamount of these components became 1000 g. They were mixed at not morethan 30 mmHg and at 130 rpm for 5 minutes. The mixture was poured into amold of 50 mm×50 mm×200 mm, and cured by heating at 80° C. for 2 hours.This was allowed to stand at room temperature for 8 hours to cool, andremoved from the mold to obtain a molded product. The evaluation resultof each molded product is shown in Table 1.

EXAMPLE 6

A polyol component and an isocyanate component were obtained in the samemanner as in Examples 1 to 5 with the mass parts specified in Table 1.

Next, while rotating the rotor of a mechanical froth machine (“MF-350mechanical froth foaming apparatus”, manufactured by TOHO MACHINERY CO.,Ltd.) at 300 rpm, the polyol component and the isocyanate component werecontinuously fed into an inlet of the mixing head in total amount of 10to 20 L/min, with a dry air at the ratio specified in Table 1.

Then, the mixture solution in which fine bubbles were disperseduniformly and which was discharged continuously through the outlet waspoured into a mold of 50 mm×50 mm×200 mm, and cured by heating at 80° C.for 2 hours. This was allowed to stand at room temperature for 8 hoursto cool, and removed from the mold to obtain a molded product. Theevaluation results of the molded product is shown in Table 1.

COMPARATIVE EXAMPLES 1 TO 3

With the mass parts specified in Table 1, molded products were obtainedin the same manner as in Examples 1 to 5. The evaluation results areshown in Table 1.

COMPARATIVE EXAMPLE 4

With the mass parts specified in Table 1, a molded product was obtainedin the same manner as in Example 6. The evaluation results are shown inTable 1.

TABLE 1 Example Comp. Example 1 2 3 4 5 6 1 2 3 4 Polyol ComponentPolyol 48.5 48.5 47.5 43.5 43.5 48.0 49.8 44.5 39.5 49.8 Microcapsules(B1) 2.5 4.8 2.5 2.5 2.5 Microcapsules (B2) 2.5 Dust-scattering reducer10.0 20.0 Inorganic filler (C1) 10.0 Hollow microsphere (C2) 5.0Dehydrating agent (C3) 0.5 0.5 0.5 0.5 0.5 0.4 1.0 1.0 0.4 Foamstabilizer (C4) 1.0 Catalyst (C5) 0.02 0.02 0.02 0.02 0.02 0.02 0.020.02 0.01 0.02 Isocyanate Component Organic polyisocyanate 48.5 48.547.5 43.5 43.5 48.0 49.8 44.5 39.5 49.8 Hollow microsphere (C2) 5.0Amount of air (volume %) 30 30 Evaluation Result of Molded ProductDensity (g/cm³) 1.15 1.16 1.14 1.27 0.95 0.85 1.17 1.15 1.13 0.84Hardness (Shore D) 87 87 86 85 79 70 88 78 70 70 Amount of scatteringdust ∘ ∘ ∘ ∘ ∘ ∘ x Δ ∘ x Bending strength (kgf/cm²) 1040 1042 1010 1100750 500 1050 820 660 505 Izod impact strength 32 31 30 30 22 15 34 16 1015 (kgfcm/cm²)

INDUSTRIAL APPLICABILITY

According to the present invention, a resin molded product for materialof a model that generates a very small amount of scattering dust whenbeing cut or ground can be obtained. When using this material, theworking environment for cutting or grinding is not contaminated by dust.Therefore, there is no fear that generated dust rides on an air streamdeveloped by rotation of a cutter and floats in the air, and scatters inthe working place over a wide range and is absorbed by a worker todamage his/her health. Also, there is no fear that generated dust entersa driving section or a control section of an NC machine to causemalfunction. Thus, the present invention has effects in maintaining thehealth of the workers and preventing problems for a cutting or grindingmachine.

Unlike the conventional method in which a dust-scattering reducer inliquid state is included in a resin, in the present invention,microcapsules containing a liquid material are put in a resin.Therefore, there is little decrease in the properties of the resin.Thus, the resin molded product obtained can be used suitably for amaterial requiring strength, such as a master model for casting or achecking fixture.

Thus, the present invention is used suitably for a resin-formingmaterial and a resin molded product for material of model that aresuitable for cutting or grinding.

1. A molded product for material of a model which is a thermosettingresin molded product wherein a total volume of 10% to 70% microbubblesof an inactive gas with respect to a volume of the molded produce aredispersed uniformly in the molded product by a mechanical froth method,and which is formed by melting and solidifying or hardening and shapinga machinable or grindable resin-forming material, that provides a resinmolded product, comprising (A) a machinable or grindable resin or aprecursor thereof; and (B) microcapsules comprising an encapsulatedmaterial (a) in liquid state at 20° C. and a wall material (b): whereinthe machinable or grindable resin-forming material includes (B) at aratio of 0.5 to 90 mass parts with respect to 100 mass arts of (A), and(a) is at least one selected from the group consisting of hydrocarbons,alcohols, esters, ketones (poly)ethers, mineral oils or purifiedproducts thereof, and animal oils, plant oils or purified or modifiedproducts thereof.
 2. A method for producing a model, which comprisescutting or grinding the molded product of claim
 1. 3. The molded productaccording to claim 1, wherein (a) comprises an organic compound having aviscosity at 20° C. of not more than 5000 mPa·s and a number-averagemolecular weight of not more than
 3000. 4. The molded product accordingto claim 1, wherein (b) is a thermosetting resin, and (a) has a freezingpoint of not higher than −5° C. and a boiling point of not lower than80° C.
 5. The molded product according to claim 1, wherein (B) have anaverage particle size of 1 μM to 1500 μm.
 6. The molded productaccording to claim 1, wherein an amount of an encapsulated oil in (B) isat least 40 volume % with respect to the volume of (B).
 7. The moldedproduct according to claim 1, wherein (A) is a hard resin with a shore DHardness of at least 60 or a precursor thereof.
 8. The molded productaccording to claim 1, wherein (A) includes at least one additive (C)selected from fillers, dehydrating agents, lubricants, foam stabilizers,defoaming agents, catalysts, coloring agents, flame retardants, ageresistors and plasticizers.
 9. In the method for producing a modelaccording to claim 2, the improvement comprising adding microcapsules(B) comprising an encapsulated material (a) in liquid state and a wallmaterial (b) into the resin molded product whereby an amount ofscattering dust when cutting or grinding is reduced.
 10. The moldedproduct according to claim 1, wherein said resin molded product has alow tendency to produce dust in the air during cutting and grinding. 11.The molded product according to claim 1, wherein the encapsulatedmaterial (a) is at least one selected from the group consisting ofhydrocarbons, alcohols, esters, ketones, mineral oils or purifiedproducts thereof, and animal oils, plant oils or purified or modifiedproducts thereof.